The invention relates to a control system for a camera. It finds particular application in conjunction with a pan/tilt head and associated methods for controlling one or more cameras and will be described with particular reference thereto. However, it is to be appreciated that the invention is also amenable to other applications. For example, the pan/tilt head may be used to control another type of payload instead of a camera payload.
In the design of any camera control system, an important factor to be considered is the camera's center of gravity (c.g.). The farther the camera's c.g. is from either motion axis (such as motion around the vertical axis, otherwise known as “pan” or motion around the horizontal axis, otherwise known as “tilt”) the more torque will be needed to move the camera to the desired location. Historically, designers of remote control pan/tilt camera heads have dealt with the issue of camera c.g. in one of two ways.
In one approach, previous designers chose one or the other (vertical or horizontal) axis and rotated the camera around its c.g. in that axis only. If the designers choose to rotate the camera around the vertical axis, then the camera is mounted on the top of the device. The problem with this design is that as soon as the camera is tilted or moved around the horizontal axis, the weight of the camera is shifted forward or backward. This weight must then be lifted in order to revert to the original position and, until that is done, the whole system of camera and mount is in an unbalanced state. This imbalance requires more motor force to move the camera. If the designers choose to rotate the camera around the horizontal axis, then the camera is mounted from the side of the device. Here, the camera may be tilted up and down without shifting its weight forward and backward, but additional torque is required to pan the camera since the c.g. of the camera is offset from the center of rotation around the vertical axis.
In other approaches, previous designs feature the camera moving both horizontally and vertically around the camera's c.g. This is done using a relatively large framework and an “L-shaped” or “U-shaped” bracket. The tilting motor and bearings are located to the side of the camera, and the panning motor and bearings are located directly below (or above) the camera. Though the camera usually remains balanced, it is at the expense of a larger and heavier support framework, which must be moved right along with the camera as it is panned.
The concept of a circular sled or cam design has existed for many years in the design of traditional pan/tilt heads for cameras in the film industry because of the requirements of large and heavy film cameras. In previous designs, the sled moves independently from the main chassis body with respect to vertical tilting around the horizontal axis, but it does not do so with respect to the panning motion. Previously, horizontal panning was initiated at the base of the entire chassis requiring that the entire assembly (camera and pan/tilt head) be moved from left to right. This is also the case with the prior camera mount configurations described above. In previous designs, the camera and its mounting plate are not isolated from the motor chassis and supporting framework with respect to motion around both the vertical and horizontal axes.
In previous motorized pan/tilt head designs, the path of the transmission of power from the motor to the camera mounting structure is along a different axis for movement in the horizontal and vertical planes. Therefore movement around one axis changes the positional relationship and the contact point between the camera mounting structure and the motor for movement around the other axis. In prior remote control pan/tilt head designs, the solution invariably chosen involved isolating the camera mounting bracket from the motor chassis and structural framework with respect to movement around the horizontal axis (tilting) while locking the camera mounting bracket to the motor chassis with respect to movement around the vertical axis (panning). In other words, when tilting, only the camera and mounting bracket moves, but when panning, the entire device, including both motors, is moved. This increases the torque requirement of the panning motor significantly. The main body of the pan/tilt head, as well as both pan and tilt motors, remain stationary as the camera and its mounting apparatus move around both the horizontal and vertical axes.
In the past, the bottom surfaces of circular sled runners have had a flat cross-section enabling it to roll smoothly over the flat races of either ball or roller bearings. Of course, free movement forward and backward over the bearings is necessary, but side to side play is undesirable.
Methods for controlling any remote control pan/tilt head have typically fallen into three categories. Most common is the “joystick” method of control. As the operator pushes a switched lever either left, right, up or down, the camera moves likewise. The problem with this method is that it is not natural for a trained camera operator. It is difficult to make gentle or subtle moves because there is no sensory feedback to your hand which signals how the camera is responding. The resultant moves invariably look very mechanical and unnatural. The second method employs a computer interface to convert either pressure on a pressure sensitive tablet or touch sensitive screen into commands for the remote control camera head. Though with practice, this is probably preferable to a joystick, it still does not provide enough feedback or information to the user to make lifelike camera moves. The third method uses an electromechanical control arm identical in size and feel to the arm on a traditional mechanical pan/tilt head. Currently, this type of electromechanical control arm has been implemented using a traditional mechanical panning head at its center. Two position encoders (one for each axis of movement) are added to this head. As the operator manipulates the mechanical pan/tilt head, the computer reads the signals from the encoders that correspond to movements in the controller head. The computer then translates these signals into movement commands for the remote control head. The camera moves exactly in tandem with the control arm. The distance the controller moves is the distance the camera moves. The speed the controller is pushed corresponds to the speed that the camera moves. This offers feedback for smooth “human” camera moves. With a joystick, typically the distance that the lever is displaced from its center is proportional to the speed at which the camera moves. There is no correspondence between the distance the joystick lever is pushed and the distance the camera moves.
Previous implementations of a computer control interface have offered little more in the way of visual feedback cues than a simple joystick. For example, as you touch a screen or pressure sensitive tablet farther away from the center of the control area the camera moves faster in that direction. This relies on the operator judging the center of the control area as he is concentrating on the picture in his monitor, which can be difficult. Particular attention is required when the operator wants to slow his camera gradually to a stop. He is required to follow an imaginary path back to the center with his finger and if he overshoots the center point of the control area even slightly, the camera image will appear to back up.
Thus, there is a particular need for improvements to existing pan/tilt equipment and methods for controlling one or more cameras in a camera system. The invention contemplates a new and improved camera control system with a pan/tilt head that overcomes at least one of the above-mentioned problems and others.